My youngest son learnt how to make these in his first year at primary school, that is how easy these little pizzas are to make. They are still a Saturday lunchtime favourite in our house, 11 years later!
Preheat the oven to 160 degrees fan. Take a plain bagel or sesame seed bagel and split in half. Spread both halves with tomato puree. Sprinkle with oregano (dry or fresh), plenty of black pepper and then top with your favourite pizza toppings. I have used lactose free cheese in the photo plus some sliced black olives. Put on a baking tray and bake for about 8-10 minutes until the cheese is melted and bubbling and the bagels are warmed through.
(You could probably do these under a low grill too, if you don’t want to use the oven.)